In this presentation we will be focusing

on the soil colour description and the silt

and clay fractions (in %).

We will be using graphs to differentiate

the soil variables, focusing on soil colour,

silt and clay fraction in percentages.

Soil colour comes from a swarm of things,

most likely, the chemical composition,

the type of bedrock that is underlain, or

the type of bedrock upslope/upstream

from where the soil was deposited and

the organic content.

RED SOIL: Red colours are due to the presence of Fe3+ or

ferric compounds and indicate that the soil is well aerated.

It indicates the accumulation of iron oxide. Mineralogy of this soil type is hematite

(Hematite is one of the most common minerals. The colour of most red and brown rock, such as sandstone,) and lepidocrocite (This mineral often occurs as an inclusion within quartz crystals. Its colour is reddish brown to a darker red, and this may vary, as it depends on what the type of quartz it is included in.)

WHITE SOIL:

White indicates the predominance of silica (quartz), or the presence of salts.

Light coloured soils may be leached (soil constituents such as organic matter, clay, or iron move downward with percolating water faster than they are added from overlying horizons), or contain high amounts of calcium carbonates.

Mineralogy of this soil type is calcite

(Calcite is a rock-forming mineral with a

chemical formula of CaCO3. It is

extremely common and found

throughout the world in sedimentary,

metamorphic and igneous rocks.)

And dolomite (is a common sedimentary

rock-forming mineral)

YELLOW SOIL:

Yellow soils signify intermediate aeration.

The mineralogy of yellow soils are goethite (is a frequent matrix material for other more aesthetic minerals. It is usually an ugly dark mineral, though specimens from a handful of locations).

And jarosite (Secondary mineral, forming under conditions of weathering in arid climates, Colourless to white in colour.)

75%

22%

3%

Red

Yellow

White

437.43

125.98

19.58

0

50

100

150

200

250

300

350

400

450

500

Red Yellow White

Silt

an

d c

lay

fra

ctio

ns

(in

%)

Soil Colour